Architects and engineers must take into account the effects not only of seismic movement, but also movements caused by building sway, settlement, thermal expansion and contraction. Architects know that any building that may be subjected to ground oscillations must be designed to control and accommodate movement caused by resonation within the structure while additionally providing for tower sway, thermal movement and settlement.
To overcome the problems associated with building movement, architects have designed buildings with various dynamic expansion joints between the walls, ceilings and floors to take into account the sway, ground motion, and settlement associated with buildings. Dynamic expansion joints are linear openings in a building designed to allow for building movement.
A disadvantage of the use of expansion joints is that they create a chimney effect in the building structure, under the conditions of a fire. Chimney effect refers to the tendency of fire and smoke to communicate through a vertical passage during a fire. Because fire is an ever-present danger in association with any building and the chimney effect at unprotected expansion joints may actually advance the communication of fire and smoke to other parts of a building, it is highly desirable to utilize a fire barrier in conjunction with any expansion joint assembly to provide additional protection to aid in the prevention of the spreading of any fire.
Fire resistant barriers have been developed that comprise layers of a suitable fire retardant material reinforced with wire mesh and/or foils. This metal reinforcement is positioned between the expansion joint and the fire resistant barrier prior to the application of the expansion joint assembly. The fire barrier is a highly thermal resistant material which protects the joint from the associated chimney effect within the building construction.
Fire barrier devices have also been designed that comprise flexible, composite barriers including a laminate of intumescent material and a backing material, such as metal foils or sheets, paper, plastic, cloth, or a mat of inorganic fibers in a binder. When exposed to heat or fire, the intumescent materials expand so as the fill open spaces in the vicinity of the architectural joint to prevent the passage of smoke, fire, water or gas.
Prior to the development of Underwriters Laboratories' test number 2079 (UL 2079) for the testing of fire resistance of building joint systems, cycling of the fire barriers before the testing of fire resistance of a fire barrier in building expansion joint applications was not required. UL test number 2079 was developed to include a cycling requirement prior to testing a building joint expansion system for fire resistance. According to the prior version of UL 2079, each building expansion joint system was required to be conditioned by subjecting the joint system to a minimum of twenty complete movement cycles to provide a condition representative of expansion joints in building structures, prior to testing for fire resistance. The conditioning requirement of UL 2079 has recently been changed to require that each building expansion joint system be conditioned for a minimum of five hundred complete movement cycles prior to testing for fire resistance.
Other prior art expansion joint treatment systems have included insulated metal foil (e.g. aluminum) layers such as those disclosed in the Fire Resistance Directory, published by Underwriter's Laboratories. Although many prior art fire barriers imply the capability to move within an expansion joint in response to normal and seismic building movement, heretofore, no prior art expansion joint fire barrier system has passed both the cycling requirement and fire resistance requirement of the new version of UL 2079. While these fire resistant barrier layers are suitable for reduction in the chimney effect associated with buildings containing expansion joints, they clearly can be improved.
LaRoche et al., U.S. Pat. No. 4,977,719, discloses a fire resistant expansion joint comprising a fire barrier comprised of a flexible fire resistant inorganic refractory fiber fabric sheet which supports resilient fire resistant inorganic refractory fibers. The flexible fire resistant inorganic refractory fiber fabric sheet is curved across its width to accommodate movement of the spaced building members.
Wilson et al., U.S. Pat. No. 5,502,937 discloses a fire protective flexible composite insulating system for either static or dynamic joints comprising a first layer material having a first and second major surface, the first layer material including inorganic fibers and a binder in the form of a flexible mat; a second layer material adhered to the first major surface of the first layer material, the second layer material consisting essentially of metal foil, and a third layer adhered to the second major surface of the first material, the third layer material including an intumescent fire retardant composite material. In a preferred embodiment, the composite insulating system comprises an insulating component, a safing component and a fire barrier component comprising a flexible composite material having a first and second portion, wherein the second portion has at least one curved portion which provides slack, thus allowing the fire barrier to effectively lengthen and shorten during relative movement of the building structure.
Landin et al., U.S. Pat. No. 5,765,332, discloses a fire barrier protected dynamic joint comprising a flexible sheet of fire barrier material and an adhesive for bonding the sheet to an attachment area of the joint. The weight of the flexible sheet of fire barrier material causes the middle region of said flexible sheet to sag within the expansion joint, providing slack for the outward expansion of the joint.
Although the above mentioned prior art fire barriers are designed to allow for relative expansion and movement of the building structure, none disclose the fire barrier and system of the present invention. Thus, there is a great need in the art of fire resistance and thermal insulation to provide a fire resistant barrier system for building expansion joints which provides adequate fire resistance under static and dynamic conditions, and which retains resiliency during normal and seismic building cycling and movement.